Composition containing supported chi-iron carbide and theta-iron carbide as well as preparation method and application of composition

Abstract

The invention relates to a composition containing load type x-iron carbide and theta-iron carbide and a preparation method and application thereof.The method comprises the steps that a load type x-iron carbide compound and a load type theta-iron carbide compound are prepared respectively, and the load type x-iron carbide compound and the load type theta-iron carbide compound are mixed; and preparing the iron carbide composition containing the supported chi-iron carbide and theta-iron carbide. According to the composition, halide ions are introduced, so that the reaction has low total CO2 selectivity in the synthesis gas conversion reaction.

Description

Technical Field

[0001] The present invention relates to the conversion of syngas, and particularly to a composition containing supported iron carbide that can be used for the conversion of syngas. Background Art

[0002] The syngas conversion technology (CO + H2) has become an increasingly important energy conversion route in recent years. After carbon-containing substances such as coal, natural gas, and biomass are gasified to obtain syngas, they can be converted into liquid fuels and high-value chemicals under the action of a catalyst.

[0003] Iron-based catalysts are commonly used catalysts, which have the advantages of high activity, a wide applicable condition window, and being suitable for industrial continuous production. However, they also have the problem of too high CO2 selectivity.

[0004] Reducing CO2 selectivity will significantly improve the carbon atom utilization efficiency, and essentially enhance the economic efficiency and environmental friendliness of the syngas conversion technology. Therefore, how to suppress the water-gas shift side reaction at high CO conversion rates, reduce CO2 selectivity, and improve the carbon atom utilization efficiency has become one of the common key problems in the field of syngas conversion. Summary of the Invention

[0005] To overcome at least one defect of the above-mentioned prior art, in a first aspect, an embodiment of the present invention provides a preparation method of a composition containing supported χ-iron carbide and θ-iron carbide, including:

[0006] Respectively prepare a supported χ-iron carbide complex and a supported θ-iron carbide complex, and mix the supported χ-iron carbide complex and the supported θ-iron carbide complex to obtain the composition containing supported χ-iron carbide and θ-iron carbide;

[0007] Wherein, the preparation process of the supported χ-iron carbide complex includes the following steps:

[0008] S11: Perform a first reduction treatment on the supported χ-precursor with hydrogen to obtain a first reduction product; the temperature of the first reduction treatment is 350 - 610 °C;

[0009] S12: Perform a surface passivation treatment on the first reduction product with an oxygen mixed gas to obtain a surface passivation product; the temperature of the surface passivation treatment is 0 - 40 °C, and the oxygen mixed gas includes 1 vol% to 3 vol% of oxygen;

[0010] S13: Subject the surface passivation product to carbide preparation treatment with a hydrogen / carbon monoxide mixture; the temperature of the carbide preparation treatment is 260 - 430 °C, and the hydrogen / carbon monoxide mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 7:1 - 110:1;

[0011] The preparation process of the supported θ - iron carbide composite includes the following steps:

[0012] S21: Subject the supported θ - precursor to a second reduction treatment with hydrogen to obtain a second reduction product; the temperature of the second reduction treatment is 330 - 580 °C;

[0013] S22: Subject the second reduction product to carbide preparation treatment with a hydrogen / carbon monoxide mixture; the temperature of the carbide preparation treatment is 330 - 430 °C, and the hydrogen / carbon monoxide mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 5.5:1 - 95:1;

[0014] Wherein, the supported χ - precursor is the iron - containing carrier including bromide ions and / or iodide ions; or, the supported χ - precursor is the iron - containing carrier, subject the surface passivation product of step S12 to impregnation treatment to make it include bromide ions and / or iodide ions, and then carry out the treatment of step S13; or, the supported χ - precursor is the iron - containing carrier, subject the product of step S13 to impregnation treatment to make it include bromide ions and / or iodide ions; the supported θ - precursor is the iron - containing carrier including bromide ions and / or iodide ions; or, the supported θ - precursor is the iron - containing carrier, subject the product of step S22 to impregnation treatment to make it include bromide ions and / or iodide ions; or,

[0015] Subject the supported iron carbide mixture to impregnation treatment with a fourth solution to obtain the iron carbide composition containing supported χ - iron carbide and θ - iron carbide; the supported iron carbide mixture includes supported χ - iron carbide and supported θ - iron carbide; wherein, use the iron - containing carrier as the supported χ - precursor to carry out the treatments of steps S11 to S13 to obtain the supported χ - iron carbide; use the iron - containing carrier as the supported θ - precursor to carry out the treatments of steps S21 and S22 to obtain the supported θ - iron carbide;

[0016] The preparation process of the iron - containing carrier includes: subject the carrier to impregnation treatment in a first solution, and subject the impregnated carrier to drying treatment and calcination treatment; the first solution contains iron ions, and the fourth solution contains iodide ions and / or bromide ions.

[0017] In a second aspect, an embodiment of the present invention provides an iron carbide composition prepared by the above-mentioned preparation method.

[0018] In a third aspect, an embodiment of the present invention provides a catalyst comprising the iron carbide composition prepared by the above-mentioned preparation method or the above-mentioned iron carbide composition.

[0019] In a fourth aspect, an embodiment of the present invention provides the application of the iron carbide composition prepared by the above-mentioned preparation method, the above-mentioned iron carbide composition or the above-mentioned catalyst in the synthesis gas conversion reaction.

[0020] In a fifth aspect, an embodiment of the present invention provides the application of the iron carbide composition prepared by the above-mentioned preparation method, the above-mentioned iron carbide composition or the above-mentioned catalyst in the reaction of synthesizing C and H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

[0021] In a sixth aspect, an embodiment of the present invention provides a synthesis gas conversion process, which includes contacting the above-mentioned catalyst with synthesis gas under reaction conditions for reaction.

[0022] The iron carbide composition of an embodiment of the present invention can be used as a catalyst for the synthesis gas conversion reaction, especially the Fischer-Tropsch synthesis reaction. By introducing halogen ions into the iron carbide, the reaction has a high CO conversion rate, an extremely low total CO2 selectivity and a low CH4 selectivity, realizing the comprehensive optimization of the reaction results. Description of the Drawings

[0023] The drawings are only for the purpose of showing specific embodiments and are not considered as a limitation to the present invention. Among them:

[0024] Figure 1 is the XRD pattern of the supported χ-iron carbide composite prepared in Example 5 of the present invention;

[0025] Figure 2 is the XRD pattern of the supported θ-iron carbide composite prepared in Example 5 of the present invention. Detailed Embodiments

[0026] Typical embodiments reflecting the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments, all of which do not depart from the scope of the present invention, and the descriptions therein are for illustrative purposes in nature and not intended to limit the present invention.

[0027] An embodiment of the present invention provides an iron carbide composition, comprising supported χ-iron carbide, supported θ-iron carbide, and halide ions; wherein the halide ions are bromide ions and / or iodide ions, and based on the number of moles of iron carbide contained in the composition, the molar content of the halide ions is 0.1 mol% to 47 mol%, and the number of moles of iron carbide is based on the number of moles of iron element contained in the composition.

[0028] In one embodiment, the iron carbide composition is formed by mixing a supported χ-iron carbide complex and a supported θ-iron carbide complex.

[0029] In one embodiment, the grain diameter of the supported χ-iron carbide or the supported χ-iron carbide complex is 3 to 28 nm, and further can be 5 to 26 nm; the grain diameter of the supported θ-iron carbide or the supported θ-iron carbide complex is 4 to 37 nm, and further can be 6 to 32 nm.

[0030] In one embodiment, the supported χ-iron carbide (or the supported χ-iron carbide complex) has a monoclinic crystal structure, and the supported θ-iron carbide (or the supported θ-iron carbide complex) has an orthorhombic crystal structure.

[0031] In one embodiment, based on the number of moles of iron carbide (100%) in the iron carbide composition, the molar content of the supported χ-iron carbide is a, and the molar content of the supported θ-iron carbide is b, wherein 0 < a ≤ 85%, 0 < b ≤ 85%, preferably, 0 < a ≤ 70%, 0 < b ≤ 70%, for example, a or b can be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 80%. Or, in the iron carbide composition, the molar content of the supported χ-iron carbide composition is a, and the molar content of the supported θ-iron carbide composition is b, wherein 0 < a ≤ 85%, 0 < b ≤ 85%, preferably, 0 < a ≤ 70%, 0 < b ≤ 70%, for example, a or b can be 1%, 5%, 10%, 15%, 20%, 30%, 50%, 80%. Wherein, the number of moles of the supported χ-iron carbide, the supported θ-iron carbide, the supported χ-iron carbide complex, and the supported θ-iron carbide complex are calculated based on the number of moles of iron element contained in each.

[0032] In one embodiment, the molar content of the halide ions is 0.1 mol% to 47 mol%, and further can be 0.6 mol% to 33 mol%, and still further can be 7 mol% to 20 mol%, for example, 0.5 mol%, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 20 mol%, 25 mol%, 30 mol%, 40 mol%.

[0033] In one embodiment, the iron carbide composition further comprises auxiliary ions, and the molar content of the auxiliary ions is from 0.1 mol% to 23 mol%, further from 0.1 mol% to 20 mol%, and still further can be from 3 mol% to 10 mol%, based on the number of moles of iron carbide contained in the composition. For example, the molar content of the auxiliary ions can be 0.5 mol%, 1 mol%, 5 mol%, 10 mol%, 15 mol%, 21 mol%.

[0034] In one embodiment, the iron carbide composition includes halide cations, and the halide cations can maintain charge balance with halide ions, that is, the total negative charge (or the total valence shown) carried by the halide ions is equal to the total positive charge carried by the halide cations.

[0035] In one embodiment, the iron carbide composition includes promoter anions, and the auxiliary ions can maintain charge balance with the promoter anions.

[0036] In one embodiment, the halide cations include one or more of first metal ions and complex cations. Further, the first metal ions include one or more of iron ions (such as divalent and trivalent iron ions), manganese ions (such as divalent manganese ions), copper ions (such as monovalent and divalent copper ions), cobalt ions (such as divalent cobalt ions), molybdenum ions (such as divalent, trivalent, and tetravalent molybdenum ions), lanthanum ions (such as trivalent and tetravalent lanthanum ions), cerium ions (such as trivalent and tetravalent cerium ions), neodymium ions (such as trivalent and tetravalent neodymium ions); the complex cations include one or more of hexaammine manganese ions, hexaammine iron ions, and hexaammine copper ions.

[0037] In one embodiment, the auxiliary ions include one or more of second metal ions. The second metal ions can include one or more of manganese ions, copper ions, cobalt ions, molybdenum ions, chromium ions, rare earth ions, alkali metal ions, and alkaline earth metal ions; for example, the second metal ions can be manganese ions (such as divalent, trivalent, and tetravalent manganese ions), copper ions (such as monovalent and divalent copper ions), cobalt ions (such as divalent cobalt ions), molybdenum ions (such as divalent, trivalent, and tetravalent molybdenum ions), chromium ions (such as trivalent chromium ions), lanthanum ions (such as trivalent and tetravalent lanthanum ions), cerium ions (such as trivalent and tetravalent cerium ions), neodymium ions (such as trivalent and tetravalent neodymium ions), sodium ions, potassium ions, calcium ions, and barium ions.

[0038] In one embodiment, the promoter anions include one or more of oxygen ions, complex ions, and acid radicals, such as nitrate, citrate, and gluconate.

[0039] One embodiment of the present invention provides a method for preparing the above iron carbide composition, including:

[0040] The supported χ-iron carbide composite and the supported θ-iron carbide composite are prepared separately, and the supported χ-iron carbide composite and the supported θ-iron carbide composite are mixed to obtain an iron carbide composition containing supported χ-iron carbide and θ-iron carbide; or,

[0041] The supported iron carbide mixture is subjected to a fourth impregnation treatment with a fourth solution to obtain an iron carbide composition containing supported χ-iron carbide and θ-iron carbide; the supported iron carbide mixture includes a supported χ-iron carbide and a supported θ-iron carbide;

[0042] Among them, the preparation process of the supported χ-iron carbide composite or the supported χ-iron carbide includes the following steps:

[0043] S11: The supported χ-precursor is subjected to a first reduction treatment with hydrogen to obtain a first reduction product; the temperature of the first reduction treatment is 350 - 610 °C;

[0044] S12: The first reduction product is subjected to a surface passivation treatment with an oxygen-containing gas mixture to obtain a surface passivated product; the temperature of the surface passivation treatment is 0 - 40 °C, and the oxygen-containing gas mixture includes 1 vol% to 3 vol% of oxygen;

[0045] S13: The surface passivated product is subjected to a carbide preparation treatment with a hydrogen / carbon monoxide gas mixture; the temperature of the carbide preparation treatment is 260 - 430 °C, and the hydrogen / carbon monoxide gas mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 7:1 to 110:1;

[0046] Among them, the supported χ-precursor is an iron-containing carrier including bromide ions and / or iodide ions that is subjected to a second impregnation treatment with a second solution, and the product obtained in step S13 is a supported χ-iron carbide composite; or, the supported χ-precursor is an iron-containing carrier, and the product obtained in step S13 is a supported χ-iron carbide; or, the supported χ-precursor is an iron-containing carrier, the surface passivated product of step S12 is subjected to a second impregnation treatment with a second solution to make it include bromide ions and / or iodide ions, and then step S13 is carried out to obtain a supported χ-iron carbide composite; or, the supported χ-precursor is an iron-containing carrier, and the product of step S13 is subjected to a second impregnation treatment with a second solution to make it include bromide ions and / or iodide ions, to obtain a supported χ-iron carbide composite;

[0047] The preparation process of the supported θ-iron carbide composite or the supported θ-iron carbide includes the following steps:

[0048] S21: The supported θ-precursor is subjected to a second reduction treatment with hydrogen to obtain a second reduction product; the temperature of the second reduction treatment is 330 - 580 °C;

[0049] S22: Subject the second reduction product to carbide preparation treatment with a hydrogen / carbon monoxide mixture; the temperature of the carbide preparation treatment is 330-430 °C, and the hydrogen / carbon monoxide mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 5.5:1-95:1;

[0050] Among them, the supported θ-precursor is an iron-containing carrier including bromide ions and / or iodide ions subjected to a third impregnation treatment with a third solution, and the product obtained in step S22 is a supported θ-iron carbide composite; or, the supported θ-precursor is an iron-containing carrier, and the product obtained in step S22 is supported θ-iron carbide; or, the supported θ-precursor is an iron-containing carrier, and the product of step S22 is subjected to a third impregnation treatment with a third solution to include bromide ions and / or iodide ions to obtain a supported θ-iron carbide composite;

[0051] The preparation process of the iron-containing carrier includes: subjecting the carrier to a first impregnation treatment in a first solution, and drying and calcining the impregnated carrier; the first solution contains iron ions, the second solution contains iodide ions and / or bromide ions, the third solution contains iodide ions and / or bromide ions, and the fourth solution contains iodide ions and / or bromide ions.

[0052] In one embodiment, the iron content in the supported precursor is 10-30 wt%, such as 12 wt%, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%.

[0053] In one embodiment, the carrier includes one or more of silica, alumina, titanium dioxide, niobium pentoxide, and zirconia. Further, the particle size of the carrier is 30-200 μm, such as 50 μm, 60 μm, 80 μm, 100 μm, 120 μm, 150 μm, 180 μm.

[0054] In one embodiment, the first solution is prepared by dissolving one or more water-soluble compounds in a first solvent, and the one or more water-soluble compounds include iron salts, and the iron salts include one or more of ferric nitrate, ferric chloride, ammonium ferrous sulfate, and ammonium ferric citrate.

[0055] In one embodiment, the first solvent includes water.

[0056] In one embodiment, the drying treatment of the carrier after the first impregnation treatment includes the following process: drying the carrier after the first impregnation treatment at 20-30 °C for 0.5-4 h, then drying at 35-80 °C and a vacuum degree of 250-1200 Pa for 6-12 h, and then drying the dried material at 110-150 °C for 3-24 h.

[0057] In one embodiment, the temperature of the calcination treatment after the drying treatment is 190 to 510 °C, such as 200 °C, 250 °C, 300 °C, 350 °C, 400 °C, 450 °C, 500 °C; and the time is 1 to 10 h, such as 2 h, 4 h, 5 h, 6 h, 8 h.

[0058] In one embodiment, the raw materials for preparing the second solution include a first halide and a second solvent, the raw materials for preparing the third solution include a second halide and a third solvent, and the raw materials for preparing the fourth solution include a third halide and a fourth solvent. Each of the first halide, the second halide, and the third halide includes a water-soluble bromide and / or iodide.

[0059] In one embodiment, each of the first halide, the second halide, the third halide, and the fourth halide independently includes one or more of bromides and iodides containing rare earth metal elements, copper, cobalt, molybdenum, manganese, and iron. Further, each of the first halide, the second halide, the third halide, and the fourth halide independently includes one or more of manganese bromide, iron(II) bromide, copper bromide, cobalt bromide, molybdenum bromide, manganese iodide, iron(II) iodide, copper iodide, rare earth bromide, rare earth iodide, hexaammine manganese bromide, hexaammine iron bromide, hexaammine copper bromide, hexaammine manganese iodide, hexaammine iron iodide, and hexaammine copper iodide.

[0060] In one embodiment, the raw materials for preparing the second solution further include a first auxiliary agent, the raw materials for preparing the third solution further include a second auxiliary agent, and the raw materials for preparing the fourth solution further include a third auxiliary agent; each of the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent may respectively include one or more of salts (organic salts and / or inorganic salts) of manganese, copper, cobalt, molybdenum, rare earth metals, alkali metals, and alkaline earth metals. For example, each of the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent may respectively be one or more of potassium nitrate, sodium nitrate, manganese nitrate, copper nitrate, cobalt nitrate, molybdenum nitrate, calcium nitrate, barium nitrate, rare earth nitrates, potassium carbonate, sodium carbonate, potassium citrate, sodium citrate, manganese citrate, copper citrate, cobalt citrate, molybdenum citrate, calcium citrate, barium citrate, potassium gluconate, sodium gluconate, lithium gluconate, rubidium gluconate, cesium gluconate, manganese gluconate, copper gluconate, and calcium gluconate.

[0061] In one embodiment, no chemical reaction occurs between the solute components of the same solution. For example, the solute of the second solution does not simultaneously include potassium carbonate and calcium nitrate.

[0062] In one embodiment, each of the second solvent, the third solvent, and the fourth solvent independently includes water and / or ethanol. For example, each of the second solvent, the third solvent, and the fourth solvent may be water or a mixture of ethanol and water.

[0063] In one embodiment, the dosages of the first halide, the second halide, the third halide, the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent can be appropriately selected according to the contents of the respective ions in the composite to be prepared. Further, the concentrations of the first halide, the second halide, the third halide, the first auxiliary agent, the second auxiliary agent, and the third auxiliary agent can all be 0.7 - 7 mol / L, such as 1 mol / L, 2 mol / L, 3 mol / L, 5 mol / L, 6 mol / L.

[0064] In one embodiment, the temperature of the first impregnation treatment, the second impregnation treatment, the third impregnation treatment, or the fourth impregnation treatment can be 0 - 50°C, further can be 20 - 30°C, such as 10°C, 15°C, 20°C, 30°C, 35°C, 40°C, 45°C, 55°C, 65°C; the time of the first impregnation treatment, the second impregnation treatment, the third impregnation treatment, or the fourth impregnation treatment can be 0.1 - 12 h, further can be 0.2 - 10 h, still further can be 0.3 - 9 h, such as 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h.

[0065] In one embodiment, the material after any impregnation treatment can be dried at 15 - 40°C, and further dried under light - shielding conditions. The drying temperature can be, for example, 20°C, 25°C, 30°C, 35°C; the drying time can be 0.5 - 12 h. The drying treatment can be carried out under normal pressure or reduced pressure.

[0066] In one embodiment, any of the above - mentioned impregnation treatments can adopt one of the slurry impregnation method, the saturated impregnation method, the supersaturated impregnation method, or other implementable impregnation methods.

[0067] In one embodiment, in the preparation of the supported χ - iron carbide composite or the supported χ - iron carbide, the temperature of the reduction treatment in step S11 can be 350 - 610°C, such as 360°C, 380°C, 400°C, 420°C, 450°C, 460°C, 480°C, 500°C, 520°C, 550°C, 560°C, 580°C, 600°C; the treatment pressure can be 0.1 - 10 atm, further can be 0.3 - 2.0 atm, such as 0.15 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.7 - 15 h, further can be 1 - 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h, 13 h.

[0068] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of H2 in step S11 can be 600 to 25000 mL / h / g, further can be 2800 to 22000 mL / h / g, such as 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 2500 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g.

[0069] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the oxygen mixture gas in step S12 comprises 1 to 3 vol% of oxygen and 97 to 99 vol% of an inert gas. The inert gas refers to a gas that does not participate in the reactions of the above steps. For example, the inert gas can be nitrogen. The content of oxygen in the oxygen mixture gas can be, for example, 1.5 vol%, 2 vol%, 2.5 vol%, 3 vol%.

[0070] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the temperature of the surface passivation treatment in step S12 can be 0 to 40 °C, such as 1 °C, 5 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C; the treatment pressure can be 0 to 1.3 atm, further can be 0 to 0.09 atm, such as 0.01 atm, 0.02 atm, 0.05 atm, 0.06 atm, 0.08 atm, 1 atm; the treatment time can be 5 to 72 h, further can be 10 to 56 h, such as 8 h, 12 h, 15 h, 20 h, 25 h, 30 h, 35 h, 40 h, 45 h, 50 h, 55 h, 60 h, 70 h.

[0071] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of the oxygen mixture gas in step S12 can be 400 to 12000 mL / h / g, further can be 1400 to 8500 mL / h / g, such as 500 mL / h / g, 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 10000 mL / h / g.

[0072] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the molar ratio of hydrogen to carbon monoxide in the hydrogen / carbon monoxide mixed gas in step S13 can be 8:1, 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, 80:1, 100:1. The hydrogen / carbon monoxide mixed gas can be a mixture of hydrogen and carbon monoxide.

[0073] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the treatment temperature in step S13 can be 260-430 °C, such as 280 °C, 300 °C, 320 °C, 330 °C, 350 °C, 380 °C, 400 °C; the treatment pressure can be 0.08-13 atm, further can be 0.15-2.5 atm, such as 0.1 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.2 atm, 1.5 atm, 1.8 atm, 2 atm, 2.2 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.3-30 h, further can be 0.5-2.4 h, such as 1 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 5 h, 10 h, 15 h, 20 h, 25 h.

[0074] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, the gas flow rate of the hydrogen / carbon monoxide mixed gas in step S13 can be 250-21000 mL / h / g, further can be 2000-18000 mL / h / g, such as 1000 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7700 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 16000 mL / h / g.

[0075] In one embodiment, in the preparation of the supported χ-iron carbide composite or supported χ-iron carbide, in step S13, the temperature of the system is raised from 0-40 °C to 260-430 °C at a heating rate of 0.1-5 °C / min, further, the temperature of the system is raised from 0-40 °C to 260-400 °C at a heating rate of 0.15-3 °C / min; the heating rate in step S13 can be, for example, 0.5 °C / min, 0.8 °C / min, 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min, 2.2 °C / min, 3 °C / min, 4 °C / min.

[0076] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the temperature of the reduction treatment in step S21 can be 330 to 580 °C, such as 350 °C, 360 °C, 380 °C, 400 °C, 420 °C, 450 °C, 460 °C, 480 °C, 500 °C, 520 °C, 550 °C, 560 °C, 580 °C; the treatment pressure can be 0.1 to 11 atm, further can be 0.3 to 2.2 atm, such as 0.15 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 2.5 atm, 5 atm, 8 atm, 10 atm; the treatment time can be 0.7 to 15 h, further can be 1 to 12 h, such as 2 h, 3 h, 5 h, 8 h, 10 h, 13 h.

[0077] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the gas flow rate of H2 in step S21 can be 600 to 25000 mL / h / g, further can be 2800 to 22000 mL / h / g, such as 1000 mL / h / g, 1500 mL / h / g, 2000 mL / h / g, 2500 mL / h / g, 3000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 8000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 20000 mL / h / g.

[0078] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the hydrogen / carbon monoxide mixture gas in step S22 includes hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide can be 5.5:1 to 95:1, such as 10:1, 20:1, 30:1, 36:1, 40:1, 50:1, 60:1, 80:1, 90:1. The hydrogen / carbon monoxide mixture gas can be a mixture of hydrogen and carbon monoxide.

[0079] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the treatment temperature in step S22 can be 330 - 430 °C, such as 330 °C, 350 °C, 380 °C, 400 °C, 420 °C; the treatment pressure can be 0 - 13 atm, further can be 0.01 - 9 atm, such as 0.1 atm, 0.2 atm, 0.5 atm, 0.8 atm, 1 atm, 1.5 atm, 2 atm, 3 atm, 5 atm, 8 atm, 10 atm, 12 atm; the treatment time can be 3 - 72 h, further can be 5 - 48 h, such as 10 h, 15 h, 20 h, 25 h, 30 h, 40 h, 45 h, 50 h, 55 h, 60 h, 70 h.

[0080] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, the gas flow rate of the hydrogen / carbon monoxide mixture gas in step S22 can be 200 - 35000 mL / h / g, further can be 1200 - 20000 mL / h / g, such as 500 mL / h / g, 1000 mL / h / g, 1800 mL / h / g, 2000 mL / h / g, 3000 mL / h / g, 4000 mL / h / g, 5000 mL / h / g, 6000 mL / h / g, 7000 mL / h / g, 10000 mL / h / g, 12000 mL / h / g, 15000 mL / h / g, 18000 mL / h / g, 25000 mL / h / g, 30000 mL / h / g.

[0081] In one embodiment, in the preparation of the supported θ-iron carbide composite or supported θ-iron carbide, in step S22, the temperature of the system is raised or lowered from the temperature of step S21 to the temperature of step S22 at a variable temperature rate (heating rate or cooling rate) of 0.2 - 5 °C / min. Further, the temperature of the system is raised or lowered to 330 - 400 °C at a variable temperature rate of 0.2 - 2.5 °C / min; the heating or cooling rate in step S22 can be, for example, 0.5 °C / min, 0.8 °C / min, 1 °C / min, 1.2 °C / min, 1.5 °C / min, 1.8 °C / min, 2 °C / min, 2.2 °C / min, 3 °C / min, 4 °C / min.

[0082] In one embodiment, preferably, the above steps and the above impregnation treatment are all carried out under light - avoiding conditions.

[0083] In one embodiment, the preparation process of the supported χ-iron carbide composite includes the following steps:

[0084] S10: Immerse the carrier in the first solution for the first impregnation treatment, and then dry and calcine the impregnated carrier to obtain an iron-containing carrier; immerse the iron-containing carrier in the second solution for the second impregnation treatment to obtain a supported χ-precursor;

[0085] S11: Carry out the first reduction treatment on the supported χ-precursor with hydrogen to obtain a first reduction product; the temperature of the first reduction treatment is 350 - 610 °C;

[0086] S12: Carry out surface passivation treatment on the first reduction product with an oxygen-containing gas mixture to obtain a surface passivated product; the temperature of the surface passivation treatment is 0 - 40 °C;

[0087] S13: Carry out carbide preparation treatment on the surface passivated product with a hydrogen / carbon monoxide gas mixture to obtain a supported χ-iron carbide composite, and the temperature of the carbide preparation treatment is 260 - 430 °C.

[0088] In one embodiment, the preparation process of the supported χ-iron carbide includes the following steps:

[0089] S10: Immerse the carrier in the first solution for the first impregnation treatment, and then dry and calcine the impregnated carrier to obtain an iron-containing carrier (i.e., the supported χ-precursor);

[0090] S11: Carry out the first reduction treatment on the supported χ-precursor with hydrogen to obtain a first reduction product; the temperature of the first reduction treatment is 350 - 610 °C;

[0091] S12: Carry out surface passivation treatment on the first reduction product with an oxygen-containing gas mixture to obtain a surface passivated product; the temperature of the surface passivation treatment is 0 - 40 °C;

[0092] S13: Carry out carbide preparation treatment on the surface passivated product with a hydrogen / carbon monoxide gas mixture to obtain the supported χ-iron carbide, and the temperature of the carbide preparation treatment is 260 - 430 °C.

[0093] In one embodiment, the preparation method of the supported θ-iron carbide composite includes the following steps:

[0094] S20: Immerse the carrier in the first solution for the first impregnation treatment, and then dry and calcine the impregnated carrier to obtain an iron-containing carrier; immerse the iron-containing carrier in the third solution for the third impregnation treatment to obtain a supported θ-precursor;

[0095] S21: Carry out the second reduction treatment on the supported θ-precursor with hydrogen to obtain a second reduction product; the temperature of the second reduction treatment is 330 - 580 °C;

[0096] S22: Subject the second reduction product to carbide preparation treatment with a hydrogen / carbon monoxide mixture to obtain a θ-iron carbide composite. The temperature for the carbide preparation treatment is 330 - 430 °C.

[0097] In one embodiment, the method for preparing supported θ-iron carbide includes the following steps:

[0098] S20: Subject the support to a first impregnation treatment in a first solution, and then dry and calcine the impregnated support to obtain an iron-containing support (i.e., a supported θ-precursor);

[0099] S21: Subject the supported θ-precursor to a second reduction treatment with hydrogen to obtain a second reduction product; the temperature for the second reduction treatment is 330 - 580 °C;

[0100] S22: Subject the second reduction product to carbide preparation treatment with a hydrogen / carbon monoxide mixture to obtain θ-iron carbide. The temperature for the carbide preparation treatment is 330 - 430 °C.

[0101] One embodiment of the present invention provides a catalyst comprising the above-described iron carbide composition.

[0102] One embodiment of the present invention provides the application of the above-described iron carbide composition or catalyst in the synthesis gas conversion reaction.

[0103] In one embodiment, the synthesis gas conversion reaction can be a Fischer-Tropsch synthesis reaction or other reactions based on the Fischer-Tropsch synthesis principle, such as a reaction with synthesis gas as the starting material and an alcohol as the final product.

[0104] In one embodiment, the synthesis gas comprises CO and H2.

[0105] One embodiment of the present invention provides the application of the above-described iron carbide composition or catalyst in the reaction for synthesizing C, H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle. Among them, the reaction based on the Fischer-Tropsch synthesis principle refers to a reaction in which a synthesis gas (a mixture of CO and H2) is used as a raw material, and through CO hydrogenation and carbon chain growth reactions under a catalyst and appropriate conditions, chain hydrocarbons and / or their oxygen-containing derivatives are generated.

[0106] In one embodiment, the above reaction is a Fischer-Tropsch synthesis reaction. The reaction temperature can be 295 - 330 °C, such as 300 °C, 305 °C, 310 °C, 315 °C, 320 °C, 325 °C; the reaction pressure can be 2 - 3.5 MPa, and the molar ratio of H2 / CO can be 1.7 - 2.15.

[0107] One embodiment of the present invention provides a syngas conversion process, which includes contacting the above-mentioned catalyst with syngas under syngas conversion reaction conditions for reaction.

[0108] In one embodiment, the syngas conversion can be carried out in a high-temperature and high-pressure continuous reactor.

[0109] The iron carbide composition of one embodiment of the present invention can be used as a catalyst for syngas conversion reaction. By introducing halogen ions into iron carbide, the reaction has a high CO conversion rate, an extremely low total CO2 selectivity, and a low CH4 selectivity. At the same time, benefiting from the very high CO space-time conversion rate of the iron carbide composition catalyst, it shows considerable activity.

[0110] The iron carbide composition of one embodiment of the present invention can be used as a catalyst for syngas conversion reaction, which can keep the reaction at an extremely low CO2 selectivity under a high CO conversion rate, while maintaining a low CH4 selectivity and a high reaction stability, greatly improving the utilization efficiency of carbon atoms and the selectivity of effective products, breaking through the key technical bottleneck, and being able to promote the high-end, diversification and low-carbon of syngas clean conversion, pointing out a new trend and direction for the development of modern syngas chemical industry.

[0111] The iron carbide composition of one embodiment of the present invention, as a catalyst for Fischer-Tropsch synthesis reaction, can maintain continuous and stable reaction for more than 300 h in an industrial Fischer-Tropsch synthesis reaction condition using a high-pressure continuous reactor, with its CO2 selectivity being below 5%, further below 3%; the selectivity of its by-product CH4 can be maintained below 8.5%, further below 5.5%; the utilization efficiency of carbon atoms is maintained above 95%, further above 97%; the selectivity of effective products can reach above 86.5%, further above 92%.

[0112] In one embodiment, through the Fischer-Tropsch synthesis reaction catalyzed by the iron carbide composition, a CO2 selectivity of <4.5%, a carbon atom utilization efficiency of >95%, and an effective product selectivity of >88% can be achieved at a CO conversion rate of 75% or more.

[0113] In this article, the "ions" contained in the complex include all particles that are combined with other particles by covalent bonds and / or ionic bonds. For example, the bromide ions in the complex include both Br that interacts with K by ionic bonds + interacting with - , and also Br atoms that interact with H atoms by covalent bonds.

[0114] The pressure values involved in this article are all gauge pressures.

[0115] The following further describes a cementite composition and its application in an embodiment of the present invention in conjunction with the accompanying drawings and specific embodiments. Among them, the involved test methods are as follows:

[0116] 1. During the reaction process of the examples or comparative examples, in-situ XRD was used to detect the phase change of the materials with an X-ray diffractometer (Rigaku Corporation, model D / max-2600 / PC), and the crystal system structures of the cementite complexes were measured by the X-ray diffractometer.

[0117] 2. The average grain diameter of each cementite or its complex was obtained by XRD testing.

[0118] 3. A Mössbauer spectrometer (Transmission 57 Fe, 57 Co(Rh) source sinusoidal velocity spectrometer) was used to perform Mössbauer spectroscopy detection on the cementite composition to obtain the corresponding composition.

[0119] 4. An inductively coupled plasma emission spectrometer (ICP) was used to detect the elements of the cementite composition.

[0120] 5. During the synthesis gas conversion reaction process, the products obtained from the reaction were subjected to gas chromatography analysis (Agilent 7890 gas chromatography) to calculate the conversion rate, selectivity, etc. The products refer to the tail gas collected from the end of the reactor, including the generated hydrocarbon compounds, alcohol compounds, CO2, etc.

[0121] 6. The CO conversion rate %, CO2 selectivity %, CH4 selectivity %, carbon atom utilization efficiency %, and effective product selectivity % were calculated by the following formulas:

[0122] CO conversion rate % = [(moles of CO in the feed - moles of CO in the product) / moles of CO in the feed] × 100%;

[0123] CO2 selectivity % = [moles of CO2 in the product / (moles of CO in the feed - moles of CO in the product)] × 100%;

[0124] CH4 selectivity % = [moles of CH4 in the product / (moles of CO in the feed - moles of CO in the product)] × 100%;

[0125] Carbon atom utilization efficiency % = (1 - CO2 selectivity %) × 100%;

[0126] Effective product selectivity % = (1 - CO2 selectivity % - CH4 selectivity %) × 100%.

[0127] Example 1

[0128] Preparation of supported χ-iron carbide

[0129] S10: Weigh 20 g of silica as the carrier, and impregnate the carrier in an aqueous solution of ammonium ferric citrate. The ammonium ferric citrate solution is weighed and prepared according to the content of 30 wt% of elemental iron in the final carrier. The impregnated carrier is dried at 30 °C for 2 h, then dried in a vacuum drying oven at 40 °C and a vacuum degree of 300 Pa for 8 h. The dried material is dried in an oven at 120 °C for 24 h, and then the obtained material is calcined in a muffle furnace at 500 °C for 5 h to obtain an iron-containing carrier, which is used as the supported χ-precursor.

[0130] S11: At a temperature of 400 °C and a pressure of 2.1 atm, the supported χ-precursor is maintained in H2 with a flow rate of 7000 mL / h / g for 7 h to carry out reduction and surface purification treatment.

[0131] S12: Cool the product of step S11 to 30 °C, and contact it with an oxygen-containing gas mixture at this temperature for surface passivation treatment. Among them, the pressure of the system is 0.06 atm, the gas flow rate is 5500 mL / h / g, and the treatment time is 21 h. The oxygen-containing gas mixture includes 1 vol% of oxygen and 99 vol% of nitrogen.

[0132] S13: Contact the product of step S12 with a hydrogen / carbon monoxide gas mixture. The pressure of the system is 2.5 atm, and the total gas flow rate is 9000 mL / h / g. Under this condition, the system is heated from 30 °C to 360 °C at a heating rate of 2.0 °C / min to carry out carbide preparation. Among them, the hydrogen / carbon monoxide gas mixture is a mixture of H2 and CO, and the molar ratio of H2 to CO is 45:1. The treatment time of the material at 360 °C is 1 h. After the treatment is completed, supported χ-iron carbide is prepared.

[0133] Preparation of supported θ-iron carbide

[0134] S20: Use exactly the same raw materials and methods as in step S10 to obtain an iron-containing carrier, which is used as the supported θ-precursor.

[0135] S21: At a temperature of 450 °C and a pressure of 2.5 atm, the supported θ-precursor is maintained in H2 with a flow rate of 10000 mL / h / g for 6 h to carry out reduction and surface purification treatment.

[0136] S22: Bring the product of step S21 into gas-phase contact with a hydrogen / carbon monoxide mixture. The pressure of the system is 5 atm, and the total gas flow rate is 7000 mL / h / g. Under these conditions, cool the system from 450 °C to 420 °C at a cooling rate of 1.5 °C / min to prepare the carbide; wherein, the hydrogen / carbon monoxide mixture is a mixture of H2 and CO, and the molar ratio of the two is H2:CO = 35:1. The treatment time of the material at 420 °C is 10 h; after the treatment is completed, supported θ-iron carbide is prepared.

[0137] Preparation of the composition

[0138] Mix the above-prepared supported χ-iron carbide and supported θ-iron carbide in a molar ratio of 2:1 (based on the molar amount of iron contained in each) to obtain an iron carbide mixture. Dissolve manganese bromide and potassium nitrate in 100 ml of water to obtain an impregnation solution. Impregnate the iron carbide mixture with the impregnation solution. The impregnation ratio is Fe:Br:K = 100:7.0:2.0, the impregnation temperature is 31 °C, and the impregnation time is 2.7 h; dry the impregnated solid material in a vacuum oven at 34 °C and a pressure of 130 Pa for 6 h to obtain an iron carbide composition, labeled as CX1.

[0139] Examples 1-1 to 3-8 are all prepared with substantially the same raw materials and processes as in Example 1, except that: the content or type of halide ions or auxiliary ions in each impregnation solution is different, and the prepared complexes are sequentially labeled as CX1-1 to CX3-8 using the same numbers as in Example 1. Since the loss of materials during the preparation process is extremely small, the content of each substance in the obtained complex is basically the same as the dosage of the corresponding raw materials. For specific content values, see Table 1.

[0140] Example 4

[0141] Preparation of supported χ-iron carbide

[0142] Supported χ-iron carbide is prepared using the same raw materials and processes as in steps S10 to S13 of Example 1.

[0143] Preparation of supported θ-iron carbide

[0144] Supported θ-iron carbide is prepared using the same raw materials and processes as in steps S20 to S22 of Example 1.

[0145] Preparation of the composition

[0146] Mix the prepared supported χ-iron carbide and supported θ-iron carbide in a molar ratio of 2:1 (based on the molar amount of iron contained in each) to obtain an iron carbide mixture. Dissolve manganese bromide, potassium citrate, and sodium nitrate in 100 ml of water to prepare an impregnation solution. Impregnate the iron carbide mixture with the impregnation solution, with an impregnation ratio of Fe:Br:K:Na = 100:15:3.0:2.0, an impregnation temperature of 35 °C, and an impregnation time of 4 h; dry the impregnated solid material in a vacuum oven at 34 °C and a pressure of 130 Pa for 6 h to obtain an iron carbide composition, labeled as CX4.

[0147] Example 4-1

[0148] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in step S13, the carbonization temperature was 260 °C. The finally obtained supported iron carbide composite was labeled as CX4-1.

[0149] Example 4-2

[0150] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in step S13, the carbonization temperature was 430 °C. The finally obtained supported iron carbide composite was labeled as CX4-2.

[0151] Example 4-3

[0152] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in the hydrogen / carbon monoxide mixture gas in step S13, the molar ratio of hydrogen to carbon monoxide was 7:1. The finally obtained supported iron carbide composite was labeled as CX4-3.

[0153] Example 4-4

[0154] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in the hydrogen / carbon monoxide mixture gas in step S13, the molar ratio of hydrogen to carbon monoxide was 100:1. The finally obtained supported iron carbide composite was labeled as CX4-4.

[0155] Example 4-5

[0156] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: the carbonization temperature in step S22 was 330 °C. The finally obtained supported iron carbide composite was labeled as CX4-5.

[0157] Example 4-6

[0158] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: the carbonization temperature in step S22 was 430 °C. The finally obtained supported iron carbide composite was labeled CX4-6.

[0159] Examples 4-7

[0160] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in the hydrogen / carbon monoxide mixed gas in step S22, the molar ratio of hydrogen to carbon monoxide was 5.5:1. The finally obtained supported iron carbide composite was labeled CX4-7.

[0161] Examples 4-8

[0162] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in the hydrogen / carbon monoxide mixed gas in step S22, the molar ratio of hydrogen to carbon monoxide was 95:1. The finally obtained supported iron carbide composite was labeled CX4-8.

[0163] Examples 4-9

[0164] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in step S11, the system pressure was 1.5 atm and the treatment time was 8 h. The finally obtained supported iron carbide composite was labeled CX4-9.

[0165] Examples 4-10

[0166] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in step S11, the treatment temperature was 400 °C and the treatment time was 6 h. The finally obtained supported iron carbide composite was labeled CX4-10.

[0167] Examples 4-11

[0168] In this example, a supported iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, except that: in step S22, the total gas flow rate was 15000 mL / h / g and the treatment temperature was 380 °C. The finally obtained supported iron carbide composite was labeled CX4-11.

[0169] Example 5

[0170] Preparation of supported χ-iron carbide composite

[0171] S10: An iron-containing carrier was prepared using exactly the same raw materials and method as in step S10 of Example 1;

[0172] Dissolve manganese bromide and potassium citrate in 150 ml of water to obtain an impregnation solution; disperse the iron-containing carrier prepared above in the impregnation solution, and perform impregnation treatment by the slurry impregnation method. The impregnation ratio (molar ratio) is Fe:Br:K = 100:7:2.0, the impregnation temperature is 30 °C, and the impregnation time is 3 h; then dry in a vacuum drying oven at 35 °C and a vacuum degree of 300 Pa for 12 h to obtain a supported χ-precursor.

[0173] Treat the supported χ-precursor with exactly the same raw materials and process as in steps S11 to S13 of Example 1 to obtain a supported χ-iron carbide composite.

[0174] Preparation of supported θ-iron carbide composite

[0175] S20: Use exactly the same raw materials and method as in step S10 to obtain a supported θ-iron carbide precursor.

[0176] Treat the supported θ-iron carbide precursor with exactly the same raw materials and process as in steps S21 to S22 of Example 1 to obtain a supported θ-iron carbide composite.

[0177] Preparation of the composition

[0178] Mix the supported χ-iron carbide composite and the supported θ-iron carbide composite prepared above in a molar ratio of 2:1 (based on the molar number of iron contained in each) to obtain an iron carbide composition, labeled as CX5.

[0179] Comparative Example 1

[0180] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, the impregnation ratio was Fe:Br:K = 100:50.0:2.0. The finally obtained iron carbide mixture was labeled as DX1.

[0181] Comparative Example 2

[0182] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, manganese bromide was not added to the impregnation solution. The finally obtained iron carbide composition was labeled as D2.

[0183] Comparative Example 3

[0184] In this example, an iron carbide composition was prepared using substantially the same raw materials and process as in Example 1, except that: in the preparation of the composition, manganese chloride in an equal amount was used to replace manganese bromide to prepare the impregnation solution. The finally obtained iron carbide composition was labeled as DX3.

[0185] Comparative Example 4

[0186] In this example, supported χ-iron carbide and supported θ-iron carbide were prepared using the same raw materials and process as in Example 1. The supported χ-iron carbide and supported θ-iron carbide were mixed in a molar ratio of 2:1 (based on the molar amount of iron contained in each) to obtain an iron carbide composition, labeled as D4.

[0187] Comparative Example 5

[0188] In this example, an iron carbide composite was prepared using substantially the same raw materials and process as in Example 1, with the only difference being that in steps S13 and S22, the molar ratio of H2 to CO in the hydrogen / carbon monoxide mixed gas was 120:1 for each. The finally obtained supported iron carbide composite was labeled as DX5.

[0189] The iron carbide composites, iron carbides, iron carbide compositions, etc. prepared in each example and comparative example were subjected to XRD, Mössbauer spectroscopy, and ICP measurements in the aforementioned manner. Among them, the total content of the target iron carbide (i.e., the total content of χ-iron carbide and θ-iron carbide) was calculated based on 100 mol, and the relevant contents all refer to the molar amount. The specific results are shown in Table 1.

[0190] In a slurry bed continuous reactor, the catalytic reaction performance of the iron carbide compositions prepared in each example and comparative example was evaluated separately. The catalyst loading was 9.0 g. Evaluation conditions: T = 286 °C, P = 2.77 MPa, H2:CO = 2.1:1, (H2 + CO) total amount = 15000 mL / h / g- Fe (standard state flow rate, relative to the Fe element), and the circulation ratio was 1.2. The reaction was carried out, and the reaction products were analyzed by gas chromatography. The reaction performance evaluation data at 24 h and 300 h of the reaction are shown in Tables 2 and 3.

[0191] Table 1

[0192]

[0193]

[0194] Table 2

[0195]

[0196]

[0197] Table 3

[0198]

[0199]

[0200] Based on the above results, when the iron carbide composition containing halogen ions such as bromine or iodine prepared in the embodiments of the present invention is used as a catalyst for the syngas conversion reaction under industrial conditions, it can exhibit ultra-low CO2 selectivity, relatively low CH4 selectivity, extremely high carbon atom utilization efficiency, and effective product selectivity while maintaining a high CO conversion rate (>60%). Further, a long-term experiment was carried out. From the data of the reaction for 300 h in Table 3, it can be seen that after the long-term continuous operation of the iron carbide composition of the embodiments of the present invention as a catalyst in a stirred tank, its CO conversion rate, product selectivity, carbon atom utilization efficiency, and effective product selectivity all remain stable without obvious changes, showing good operation stability. Therefore, by using the iron carbide composition of the embodiments of the present invention as a catalyst for the syngas conversion reaction, comprehensive optimization of the reaction results can be achieved.

[0201] Unless otherwise specified, the terms used in the present invention have the meanings commonly understood by those skilled in the art.

[0202] The embodiments described in the present invention are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. Those skilled in the art can make various other substitutions, changes, and improvements within the scope of the present invention. Therefore, the present invention is not limited to the above embodiments but is only defined by the claims.

Claims

1. A method for preparing an iron carbide composition containing supported χ-iron carbide and θ-iron carbide, comprising: The supported χ-iron carbide composite and the supported θ-iron carbide composite are prepared separately, and the supported χ-iron carbide composite and the supported θ-iron carbide composite are mixed to obtain the iron carbide composition containing supported χ-iron carbide and θ-iron carbide; Among them, the preparation process of the supported χ-iron carbide composite includes the following steps: S11: The supported χ-precursor is subjected to a first reduction treatment with hydrogen to obtain a first reduction product; the temperature of the first reduction treatment is 350-610 °C; S12: The first reduction product is subjected to a surface passivation treatment with an oxygen-containing gas mixture to obtain a surface passivated product; the temperature of the surface passivation treatment is 0-40 °C, and the oxygen-containing gas mixture includes 1 vol% to 3 vol% of oxygen; S13: The surface passivated product is subjected to a carbide preparation treatment with a hydrogen / carbon monoxide gas mixture; the temperature of the carbide preparation treatment is 260-430 °C, and the hydrogen / carbon monoxide gas mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 7:1 to 110:1; The preparation process of the supported θ-iron carbide composite includes the following steps: S21: The supported θ-precursor is subjected to a second reduction treatment with hydrogen to obtain a second reduction product; the temperature of the second reduction treatment is 330-580 °C; S22: The second reduction product is subjected to a carbide preparation treatment with a hydrogen / carbon monoxide gas mixture; the temperature of the carbide preparation treatment is 330-430 °C, and the hydrogen / carbon monoxide gas mixture includes hydrogen and carbon monoxide with a molar ratio of H2:CO = 5.5:1 to 95:1; Among them, the supported χ-precursor is the iron-containing carrier including bromide ions and / or iodide ions; or, the supported χ-precursor is the iron-containing carrier, and the surface passivated product of step S12 is impregnated to make it include bromide ions and / or iodide ions, and then the treatment of step S13 is carried out; or, the supported χ-precursor is the iron-containing carrier, and the product of step S13 is impregnated to make it include bromide ions and / or iodide ions; the supported θ-precursor is the iron-containing carrier including bromide ions and / or iodide ions; or, the supported θ-precursor is the iron-containing carrier, and the product of step S22 is impregnated to make it include bromide ions and / or iodide ions; or, The supported iron carbide mixture is impregnated with a fourth solution to obtain the iron carbide composition containing supported χ-iron carbide and θ-iron carbide; the supported iron carbide mixture includes supported χ-iron carbide and supported θ-iron carbide; among them, the iron-containing carrier is used as the supported χ-precursor to carry out the treatments of steps S11 to S13 to obtain the supported χ-iron carbide; the iron-containing carrier is used as the supported θ-precursor to carry out the treatments of steps S21 and S22 to obtain the supported θ-iron carbide; The preparation process of the siderophore includes: impregnating the carrier in a first solution, and drying and calcining the impregnated carrier; the first solution contains iron ions, and the fourth solution contains iodide ions and / or bromide ions.

2. The preparation method according to claim 1, wherein The first solution is prepared by dissolving one or more water-soluble compounds in a first solvent, and the one or more water-soluble compounds include one or more of ferric chloride, ferric nitrate, ammonium ferric citrate, and ammonium ferrous sulfate; or, The supported χ-precursor is obtained by subjecting the siderophore to a second impregnation treatment with a second solution; or, the product of step S12 or the product of step S13 is subjected to the second impregnation treatment with the second solution; The supported θ-precursor is obtained by subjecting the siderophore to a third impregnation treatment with a third solution; or, the product of step S22 is subjected to the third impregnation treatment with the third solution; the second solution contains iodide ions and / or bromide ions, and the third solution contains iodide ions and / or bromide ions.

3. The preparation method according to claim 2, wherein The drying treatment includes: drying the carrier after the first impregnation treatment at 20-30°C for 0.5-4 h, then drying at 35-80°C and 250-1200 Pa for 6-10 h, and then drying the dried material at 110-150°C for 3-24 h; and / or, The carrier is selected from one or more of zirconia, silica, niobium pentoxide, titanium dioxide, and alumina; and / or, The raw materials for preparing the second solution include a first halide and a first auxiliary agent. The first halide includes one or more of bromides and iodides containing rare earth metal elements, copper, cobalt, molybdenum, manganese, and iron. The first auxiliary agent includes one or more of salts of manganese, alkali metals, molybdenum, rare earth metals, copper, alkaline earth metals, and cobalt; and / or, The raw materials for preparing the third solution include a second halide and a second auxiliary agent. The second halide includes one or more of bromides and iodides containing rare earth metal elements, copper, cobalt, molybdenum, manganese, and iron. The second auxiliary agent includes one or more of salts of manganese, alkali metals, molybdenum, rare earth metals, copper, alkaline earth metals, and cobalt; and / or, The raw materials for preparing the fourth solution include a third halide and a third auxiliary agent. The third halide includes one or more of bromides and iodides containing rare earth metal elements, copper, cobalt, molybdenum, manganese, and iron. The third auxiliary agent includes one or more of salts of manganese, alkali metals, molybdenum, rare earth metals, copper, alkaline earth metals, and cobalt; and / or, The temperature of the calcination treatment is 190-510°C, and the particle size of the carrier is 30-200 μm.

4. An iron carbide composition prepared by the preparation method according to any one of claims 1 to 3.

5. The composition according to claim 4, comprising supported χ-iron carbide, supported θ-iron carbide and halide ions; wherein The halide ion is bromide ion and / or iodide ion. Based on the number of moles of iron carbide contained in the composition, the molar content of the halide ion is 0.1 mol% to 47 mol%, and the number of moles of iron carbide is calculated based on the number of moles of iron element contained in the composition.

6. The composition according to claim 5, wherein The composition further includes auxiliary ions, and the molar content of the auxiliary ions is from 0.1 mol% to 23 mol%, further from 0.1 mol% to 20 mol%; the auxiliary ions include one or more of second metal ions, and further, the auxiliary ions include one or more of alkaline earth metal ions, molybdenum ions, rare earth ions, cobalt ions, manganese ions, chromium ions, copper ions, and alkali metal ions; and / or, The molar content of the halogen ions is from 0.6 mol% to 33 mol%.

7. A catalyst comprising the iron carbide composition prepared by the preparation method according to any one of claims 1 to 3 or the iron carbide composition according to any one of claims 4 to 6.

8. Use of the iron carbide composition prepared by the preparation method according to any one of claims 1 to 3, the iron carbide composition according to any one of claims 4 to 6 or the catalyst according to claim 7 in a syngas conversion reaction.

9. Use of an iron carbide composition prepared by the preparation method according to any one of claims 1 to 3, an iron carbide composition according to any one of claims 4 to 6, or the catalyst according to claim 7 in a reaction for synthesizing C, H fuels and / or chemicals based on the Fischer-Tropsch synthesis principle.

10. A syngas conversion process, comprising contacting the catalyst according to claim 7 with syngas under reaction conditions for reaction.

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